This invention relates to multiple-lane conversion systems. It is particularly adapted for conversion systems making easy open can ends.
Presses for converting ends for cans generally comprise a press bed having columns supporting a crown. The crown houses a drive for a reciprocating ram which slides on ways formed in the columns. The ram carries upper tooling which cooperates with lower tooling mounted on the bed. The tooling defines a plurality of lanes and stations in which shells are progressively converted into easy open can ends. A conveyor carries the shells into and through the stations of the tooling. A press of this character is shown and described in Herdzina, U.S. Pat. No. 5,017,072, the disclosure of which is incorporated herein by reference.
One of the stations is a score station wherein a score and anvil cooperate to partially cut through the end, thereby defining the frangible portion of the can that will open upon actuation of a tab. The thickness of the end at the scored line is called the residual. Obviously that thickness must be carefully controlled so that the end will properly protect the contents of a can until it is opened, at which time the scored portion must give way under the influence of the user's actuation of the tab.
The residual thickness depends on the separation of the score and anvil at their closest approach. In the past this distance was controlled by the use of mechanical shims placed in the support structure for one or both of the score and anvil. Obtaining the proper residual required installation of the correct thickness of shims and this was done by a process of trial and error. The press had to be stopped, the tools taken out, the shims put in, the tools reinstalled and the results tested. It was possible for adjustment of one lane to throw another one out of specification. Then that other one had to be adjusted, all with the consequent loss of production due to the downtime. Of course, redressing the scores required redoing the entire setup operation.
At a time when presses were running two lanes at about 225 strokes per minute the shim construction was acceptable. Now, however, presses having four to six lanes are running at 550 to 600 strokes per minute. At that rate of production it becomes very difficult to get the score stations in all lanes simultaneously set up and operating properly.